simpleBob
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 Sep11 comment $F(\frac{1} {x})=x^3 - 2$; what is $F(\frac{x} {y})$? In mathematics, you should not assume definitions that are not given. The question does not define the function to be f:ℝ->ℝ. And it obviously has a value that is undefined, that does not make the result be wrong. Note that the result of this function may not stay that way, the function may be transformed and the undefined result may suddenly become a well-formed result. Sep11 comment $F(\frac{1} {x})=x^3 - 2$; what is $F(\frac{x} {y})$? @user37238 I also can define functions with undefined results. For example, division would be one of those functions. f(x,y)=x/y may be undefined for y=0 Sep11 comment $F(\frac{1} {x})=x^3 - 2$; what is $F(\frac{x} {y})$? @user37238 If I define a function as f(x)=x/0, what would be f(5)? Sep11 comment $F(\frac{1} {x})=x^3 - 2$; what is $F(\frac{x} {y})$? @user37238 Division by zero may be undefined (depending on the mathematical setting), but it is not incorrect. Sep11 comment $F(\frac{1} {x})=x^3 - 2$; what is $F(\frac{x} {y})$? @RobertLewis It would also be correct for x=0. Why should it be wrong?, also 0! = 1 :P Jul17 awarded Supporter Jul17 comment How to convince a math teacher of this simple and obvious fact? Absurdity is actually the correct word. Since it was demostrated by "Reductio ad absurdum". Upvote, I learned something new :) Jul17 comment How to convince a math teacher of this simple and obvious fact? it is not absurd, it is a contradiction. Just saying... Apr11 comment What is the real life use of hyperbola? hyperbolas in real life Apr16 awarded Autobiographer